Release time：2020-01-16 18:44 Browse：
### 1. **Standard & Dimensional Compliance** - Manufactured to **GB5787** (Chinese national standard), governing key parameters: flange diameter/height, thread length, and shank tolerance for hexagon flange bolts. - Ensures interchangeability with standard components, with dimensional accuracy controlled within ±0.1mm for critical features (e.g., flange thickness, thread pitch). ### 2. **Material & Mechanical Properties** - **Base Material**: Medium-carbon alloy steel (typically 40Cr or 35CrMo), heat-treated to achieve **Grade 8.8** performance: - Tensile strength: ≥800 MPa - Yield strength: ≥640 MPa - Hardness: 22–32 HRC (Rockwell C scale), balancing strength and ductility for heavy-duty loads. - Suitable for applications requiring high clamping force, such as machinery frames or structural joints. ### 3. **Key Design Features** #### - **Hexagon Flange with Serrated Teeth** - Integral flange (one-piece design) eliminates the need for separate washers, reducing assembly time. - **Toothed flange surface**: Small serrations (teeth) bite into the mating surface during tightening, preventing loosening under vibration (common in automotive or industrial equipment). #### - **Extended Length** - Shank length exceeds standard GB5787 dimensions, customizable from 50mm to 500mm, ideal for fastening thick materials (e.g., multi-layer steel plates, engine blocks) or deep recesses. ### 4. **Surface Treatment: Blue-White Zinc Plating** - **Process**: Electroplated zinc coating (5–15μm thickness) followed by blue-white chromate passivation, forming a protective film. - **Benefits**: - Corrosion resistance: Withstands ≥48 hours in salt spray testing (ASTM B117) without red rust, suitable for indoor/outdoor use. - Aesthetic finish: Bright blue-white appearance, often used in visible applications (e.g., machinery exteriors). - Lubricity: Reduces galling during installation compared to unplated bolts. ### 5. **Thread Specifications** - **Metric threads**: M5 to M30 (coarse pitch per GB/T 196), with 6g external thread tolerance for precise fit with nuts or tapped holes. - **Thread type**: Rolled threads (not cut), enhancing fatigue strength by 20–30% through work hardening of the thread surface. ### 6. **Applications** - **Automotive industry**: Engine mounts, chassis components, or suspension systems (relying on anti-vibration toothed flange). - **Industrial machinery**: Heavy equipment frames, conveyor systems, or press tools (using extended length for thick assemblies). - **Construction**: Structural steel connections or prefabricated modules requiring high-strength, corrosion-resistant fastening. ### 7. **Quality & Testing** - **Mechanical testing**: Each batch undergoes tensile, yield, and hardness testing to verify Grade 8.8 compliance. - **Dimensional checks**: Thread gauging (GO/NO-GO) and flange tooth depth inspection to ensure anti-loosening performance. - **Plating verification**: Adhesion testing (tape test per ASTM B571) and thickness measurement via X-ray fluorescence. ### 8. **Handling & Storage** - Protected from moisture during storage to preserve blue-white plating; recommended to use within 12 months of production for optimal corrosion resistance. - Compatible with standard hex wrenches for installation, with flange teeth requiring controlled torque (typically 20–50 N·m, depending on bolt size) to avoid damaging mating surfaces.
